Brush holder



E. C. KUHN BRUSH HOLDER Feb. 21, 1961 2 Sheets-Sheet 1 Filed May 5, 1959 n .n m m M EC V n Nr ,T I A 7 Y. B

WITNESSES 42 71' Feb. 21, 1961 c, KUHN 2,972,689

BRUSH HOLDER I Filed May 5, 1959 2 Sheets-Sheet 2 Fig.3

nited States Patent BRUSH HOLDER Earl C. Kuhn, Penn Hills Township, Allegheny County, Pa., assignor to Westinghouse Eiectric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed May 5, 1959, Ser. No. 811,163

8 Claims. (Cl. 310-246) This invention relates to an improved brush holder for dynamoelectric machines, and more particularly, to an improved pressure finger assembly for a brush holder.

Recent developments in the spring art have made it possible to provide constant force brush holders in which no adjustment is required during the life of the brush. These developments include a pre-stressed coil spring which is so pre-stressed as to naturally wind into a free type volute. This type of spring has been disclosed for use in a brush holder. These prior art devices employ such a spring with the free end secured to a wall of the brush holder with the volute in engagement with the upper end of the brush. The pressure thus exerted by the spring causes the brush to engage the surface of the commutator or slip rings as the case may be at a substantially constant predetermined pressure throughout the life of the brush. In other known forms, the volute is secured by various means adjacent the lower end of the brush holder. The free end of the constant force spring engages the upper portion of the brush. Again the pressure exerted by the spring causes the brush to engage the surface of the commutator or slip rings at a substantially constant predetermined pressure throughout the life of the brush. In other modifications known to the prior art this type of spring is secured to a mounting member which is removably clipped on to a portion of the brush holder. In this latter modification, the free end of the spring is secured to the spring mounting member and the mounting member is so secured to the brush holder that the volute of the spring engages the upper portion of the brush.

In these prior art devices, the constant force coil spring is successfully employed to exert substantially constant force on the brush throughout its life. However, certain disadvantages are inherent in these constructions. With the volute directly engaging the surface of the brush relative motion between the brush and the volute occurs. As the volute rewinds itself, it rubs on the surface of the brush. This may cause fretting corrosion of the spring. This fretting corrosion may change the characteristics of the spring, thus rendering it no longer a constant force spring.

Another difiiculty encountered in the prior art devices is that of removing and replacing a brush when it is so worn that it is no longer useful. This requires the operator to remove the spring from the surface of the brush with one hand and to hold the spring in an inoperative position, While with the other hand, he must remove the remnant of the old brush, dispose of it, pick up a new brush and insert it in the brush holder. This involves a risk to the person servicing the machine, as well as the possibility of injury to the machine. It is conventional practice, particularly in large generating equipment, to replace the brush while the machine is operating. Should the operator accidentally release the constant force spring while replacing a new brush, there is danger of the spring falling into the path of the rotating parts of the machine. Another serious disadvantage is the possibility of the 2,972,689 Patented F eh. 21, 1961 spring detaching itself from the means securing it to the brush holder and falling into the machine. In the modification in which a spring is secured to a separate mount which is in turn removably secured to the brush box, the person servicing the machine can remove the spring from the surface of the brush and it will remain out of engagement with the brush, eliminating the necessity for him to employ one hand to hold it out of engagement. However, in this modification, there is a possibility that due to the vibratory motion inherent in the machine the spring mounting clip can become disengaged. This will result either in the spring being accidentally moved to an inoperative position or the spring and its mount becoming disengaged from the brush holder and falling into the rotating parts of the machine. In all of the prior art devices, the constant force spring directly engages the brush and the possibility of fretting corrosion becomes a serious problem.

In carrying out the present invention, the abovedescribed disadvantages are eliminated by providing a separate carrier for a pressure finger which enables the pres sure finger to be mounted in such a position that relative motion between the surface of the brush and the pressure finger will not occur. The use of a flexible pressure finger overlying the upper end of the brush permits the pressure finger to follow the vibratory motion of the brush Without slip and relative motion, and hence eliminates a probable cause of fretting corrosion. The vibratory motion is clamped in the flexible pressure finger and is prevented thereby from being transmitted to the carrier and spring. The constant force spring is employed in such a manner that it cannot become a freely movable object. Rather than employing a constant force spring to directly engage the brush, the constant force spring is employed to exert a downward force on the movable carrier which carries the pressure finger.

The principal object of the present invention is to provide an improved brush holder for dynamoelectric machines which requires no adjustment'for the life of the brush, which is designed to facilitate replacement of the brush, and which eliminates a probable cause of fretting corrosion of the constant force spring.

Another object of the invention is to provide an improved brush holder for dynamoelectric machines which employs a flexible pressure finger designed to avoid rela tive motion between the finger and the brush and in which the pressure finger is urged into contact with the brush by a constant force spring, thereby eliminating a probable cause of fretting corrosion as well as the need for adjustment for the life of the brush.

A further'object of the invention is to provide an improved brush holder for dynamoelectric machines which utilizes a pressure finger urged into engagement with the brush by a substantially constant force spring and which may be easily removed to an inoperative position and retained out of engagement with the brush for simple and safe brush replacement.

A still further object of the invention is to provide an improved brush holder for a dynamoelectric machine which requires no adjustment for the life of the brush and in which no parts are free to drop onto a moving part of the machine during operation, during replacement of a brush, or in case of a broken spring.

Other objects and advantages of the invention will be apparent from the following detailed description, taken in connection with accompanying drawings, in which:

Fig. 1 is a side elevation view of a brush holder, partly in longitudinal section taken on line 1-1 of Fig. 2;

Fig. 2 is a top elevation view of the brush holder of Fig. 1, partly in transverse section;

Fig. 3 is a side elevation view of another embodiment of the invention, partly in section taken on line III-III of Fig. 4; and

Fig. 4 is atop elevation view of the modification shown in Fig. 3, partly in section.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts through out the several views, there is shown in Figs. 1 and 2 a brush holder 1i arranged for positioning adjacent a r tating current collector 12 such as a commutator or slip ring as the case may be (shown schematically) for a dynamoeleotric machine. The brush holder it) includes a brush housing or box 14 open at both ends andfon one side. The brush housing 14 is shown as being of hollow rectangular shape, but it will be understood that it may be of any suitable shape. The brush housing 14 receives a brush 16. Secured to the wall opposite the open side of the brush housing 14 is a bracket 18 adapted for attachment to a supporting structure (not shown). A pressure finger assembly 20 is provided which includes a carrier 22. Secured to the carrier 22 is a flexible finger 24 which extends downwardly to a point below the carrier 22 and is in longitudinal alignment with the brush 16. The flexible pressure finger 24 is connected to the carrier through a connecting arm 26. The connecting arm 26 may be used as a handle to enable the operator to manipulate the pressure finger from operative to inoperative position and vice versa. The carrier 22, connecting arm or handle 26 and pressure finger .24 may be integral, as shown, or any suitable means may be utilized to secure these parts together.

The carrier 22 comprises a pair of parallel arms 23 and 25. At each end of each of the arms are circular openings 27. The openings 27 at corresponding ends of the arms 23 and 25 are in alignment. A roller axle 28 carrying a roller 32 is received between the arms 23 and 25 and extends through the openings 27 at the end of the carrier adjacent the pressure finger 24. A roller axle 34 is received between the arms 23 and 25 and extends through the openings 27 adjacent the end of the carrier remote from the pressure finger 24. The roller axle 39 has a roller 34 journaled thereon. The axles 28 and 3%) may be secured in position on the carrier in any suitable manner as for example, by retaining rings 36 as shown.

A guideway assembly 40 is secured to the brush hous ing 14 and spaced therefrom. The guideway assembly 49 is secured at its lower end to the lower end of the open side of the brush housing 14 either integrally as shown or by welding, or in any suitable manner. The

guideway assembly 4% includes a front wall 42 which is secured at its lower end 44 to the lower end of the open wall of the brush housing 14. It extends parallel to the open wall of the brush housing 14 and is spaced laterally therefrom for its entire length, except for the broad lower portion 44 which is rigidly secured to the brush holder. The front wall 42 has a pair of flanges 46 and 48 at each longitudinal edge extending rearwardly away from the brush housing 14. Guideway assembly 40 is provided with a rear wall 59 which is parallel to the front wall 42. Rear wall 51) is slightly Wider than front wall 42 and extends laterally outward beyond wall 42 at each side. Projecting forwardly from each side edge of Wall 56 are a pair of flanges 52 and 54, one of these flanges projecting from each edge toward the brush holder and extending to a point in alignment with the front side of the front wall 42. These flanges 52 and 54 form a protective cover at the sides of the guideway 40. Intermediate the side walls 52 and 54, and rigidly or integrally secured to the rear wall 50, are a pair of longitudinally extending projections or tracks 56 and 58. These tracks 56 and 58 are opposed to and in alignment with front wall flanges 46 and 48 respectively.

At the upper end of the guideway assembly 4% and extending from rear wall 50 to front wall 42 is an upwardly and rearwardly inclined connecting portion s which forms an extension of front wall 42. The inclined portion 60 is equal in width to the front wall 42. Intermediate the front and rear walls 42 and on connecting portion 61 is a transverse recessed portion 62 extending from one edge to the other. The front side of front wall 42 and the upper side of inclined connecting portion 60 form a guideway or track for roller 32 of carrier 22. The flanges 46 and 48 and the tracks and 58 form a trackway or guideway for the roller 34. The carrier 22 is disposed on the guideway assembly 25 with its parallel arms receiving the front Wall there'oetween intermediate the rollers 32 and 34. The roller 32 engages and is movable on the front of front wall 42. The roller 34 engages and is received between the flanges 46 and 48 and the tracks 56, 58. With the carrier 22 so positioned, the pressure finger 24 extends downwardly and in overlying engagement with the brush 16, as can be clearly seen in Figs. 1 and 3.

A coiled spring 64 of width smaller than the distance between flanges 46 and 48 has its free end 66 secured to the lower portion 44 intermediate the tracks 46 and 48. The spring 64 may be secured in any suitable manner, as for example, by rivets 67 as shown in Fig. 1. The flat unwound portion of the spring extends upward along the rear side of front wall 42 between the flanges 46 and 48 and the volute 68 of spring 64 is disposed about the roller 34. The spring 64 is a self-rewinding spring which is prestressed so as to naturally wind into a free tight volute. The force exerted by the spring is substantially constant and independent of the distance between the volute and the free end 44.

Thus, it can be seen that the spring urges the carrier 22 downwardly, thus causing the pressurevfinger 24 to bear on the upper end of brush 16 thereby biasing the brush 16 against the commutator or slip ring 12 with a constant pressure. During operation of the machine, the portion of the brush bearing against the collector 12 wears down. As it wears down, the pressure finger 24 will continue to urge the brush against the collector with. a substantially constant pressure since the carrier is being urged downwardly with a constant pressure. Any vibratory motion will be absorbed by the flexible pressure finger 24 and will not be transferred to the carrier 22 or spring 64. When it is desired to replace a brush or otherwise remove the pressure finger from operative position the person servicing the equipment can with one finger grasp the pressure finger assembly 20 at the connecting arm or handle portion 26 and exert an upward force thereon. The roller 32 will roll up the outside of wall 42 and upwardly and outwardly on the inclined portion 60, until it drops into the recess 62. It will then be retained in an inoperative position, as shown by dotted lines in Fig. 1. The operator may then release his grasp from the pressure finger assembly and proceed to remove the brush 16 and replace it. He then may grasp the handle portion 26 of spring finger assembly 24 and exert a slight upward and forward force removing the roller from the recess portion 62 and engage the roller 32 on the inclined portion 60. The spring will then act to exert a force on the carrier 22 to cause the pressure finger 24 to engage the brush 16.

From the above description and drawing, the advantages of this novel construction are apparent. Should the spring 64 accidentally become detached at rivets 67 the spring will rewind itself on the carrier 22. There is no possibility that it would fall into the rotating parts of the machine. Should the spring break at any point, a portion will be retained by the rivets 68 and the remaining portion will rewind itself on the carrier 22. The advantages of a constant force spring are utilized but the need for engaging this spring directly on the brush 16 is eliminated by use of the pressure finger assembly. Thus, probable causes of fretting corrosion due to sliding and relative motion between the spring and the brush are eliminated. Since the flexible pressure finger 24 bears downwardly on the upper surface of the brush, and since there can be no relative sliding motion between the brush 16 and the spring finger 24, there can be no fretting corrosion on the pressure finger due to relative motion between brush and finger. The pressure finger assembly 20 can easily and with one hand be drawn into an inoperative position and so retained by recess 62.

The embodiment of the invention shown in Figs. 3 and 4 differs from the Fig. 1 embodiment only in the construction of the guideway and the rollers on the free end of the carrier. In order to eliminate unessential detailed description only those parts which differ will be described in detail. The same reference numerals will be employed for like parts.

The brush holder includes a brush housing 14 which receives a brush 16, which brush is urged against the rotating collector 12 by pressure finger 24. A pressure finger assembly is provided, which includes the pressure finger 24 and a connecting arm or handle 26 for connecting the pressure finger 24 to a carrier 22'. Carrier 22 includes a pair of parallel arms 23 and 25 and roller axles 28 and 30 which extend between carrier arms 23 and 25 and through openings 27 adjacent the ends of the carrier arms. A roller 32 is carried on roller axle 28. The axles 28 and 30 are retained in position by retaining rings 36. Thus far, the Fig. 3 embodiment is identical to the Fig. l embodiment.

The embodiment shown in Fig. 3 includes a trackway or guideway having a lower portion 44 which is secured to the lower end of the open rear side of brush housing 14. It also includes an intermediate portion 42 which is spaced rearwardly from the rear side of brush housing 14 and extends longitudinally parallel thereto and terminates in a rearwardly and upwardly inclined portion having a transverse recess 62'. The carrier 22 has mounted on its axle 30 a pair of rollers 34a and 34b, and one of these rollers is mounted for rotation at each end of the axle 30. The guideway 42 is received between the arms 23 and 25 of the carrier 22' intermediate the roller axles 28 and 30. The roller 32 rides on the front surface of the intermediate portion 42 and the inclined portion 60' of the guideway assembly 40. 'The rollers 34a and 34b ride on the rear surface of the intermediate portion 42' and inclined portion 60 of the guideway assembly 40. The volute 68 of a self-rewinding constant force coil spring receives in its open center portion the axle 30 of the carrier 22. The volute is disposed between the rollers 34a and 34b. The free end 66' of the coil spring 64' extends down along the rear side of the guideway assembly 40 and under the lower edge thereof. A cover 70 has rear wall 72 and side walls 74 and 76 and a bottom wall 77. The cover 70 is disposed with the side walls facing forwardly enclosing the guideway assembly 40' and the rear wall extending parallel to the portion 42 of the guideway assembly 40'. extends forwardly from the upper end of the rear wall and engages the inclined surface 60. A pair of lower tabs 79 extend inwardly from each side of the bottom wall 77 and engage the lower end of the connecting portion 44 of the guideway, thereby retaining the cover and the free end of the coil spring in place. Although unlikely, should the spring 64' break in more than one place leaving free fragments, such fragments will be prevented from falling into the rotating parts of the machine by bottom wall 77 of cover 70.

The operation of the brush holder assembly is similar to the operation of the embodiment disclosed in Fig. l. The carrier 22 and its associated pressure finger 24 are biased downward by the coil spring 64 with constant force. The pressure finger 24 bears against the brush 16 urging it toward the commutator, or slip ring 12 with substantially the same force regardless of brush wear. When it is desired to replace the brush or remove the pressure assembly from the operative position, the operator grasps the handle 26 of the pressure finger A tab 78 assembly, thereby exerting a rearward and outward force moving the roller 32 into recess 62' where it will be retained until a force is applied by the operator to move it back into operative position. When it is desired to again restore the pressure finger to operative position the operator need merely grasp the handle 26 and apply a slight force to move the roller 32 out of the recess 62. The constant force spring 64 will then take over to urge the carrier downward causing the pressure finger to exert a downward force on the brush 16.

All of the advantageous features of the Fig. l embodiment are retained. In addition the cover 70 offers further protection against loose parts falling into the rotating portions of the machine. The pressure finger 24 engages the brush 16 and bears thereagainst regardless of brush wear with a substantially constant force without any relative sliding motion between the two. Thus, there is no fretting corrosion due to sliding motion. No contact between the spring 64 and the brush 16 is required. Vibratory motion is damped by the flexible pressure finger 24. The pressure finger assembly may easily be moved to operative position with one hand by the person servicing the machine. It may be retained in an operative position relieving the operator of the necessity of handling it in an inoperative position.

It should now be apparent that an improved brush holder for a dynamoelectric machine has been provided which requires no adjustment for the life of the brush, which is designed to facilitate replacement of the brush, and which eliminates fretting corrosion, of a substantially constant force spring due to relative sliding motion. As previously pointed out, no parts under any circumstances are free either by accident or failure to interfere with the rotating portionsof the machine.

Certain preferredembodiments of the invention have been shown and described for the purpose of illustration, but it will be apparent that various modifications may be made, as for example, other retaining means than the recess 62 may be employed on the inclined surface 60, anti-friction means other than rollers may be used on the carrier, and other diiferent means may be employed to secure the free end of the constant force spring to the guideway assembly. It is to be understood that the invention in its broadest aspects is not limited to the specific details of construction shown and described, but includes all equivalent embodiments and modifications which come within the scope of the invention.

I claim as my invention:

1. A brush holder for a dynamoelectric machine comprising an open ended housing for receiving a brush, a pressure finger assembly for urging said brush into contact with a rotatable member, said pressure finger assembly including a flexible pressure finger overlying said brush and bearing thereon when in operative position to urge said brush toward said rotatable member, a movable carrier for said pressure finger, a stationary guideway for said carrier, and a substantially constant force spring terminating in a self-rewinding volute, said volute being mounted on said carrier and the free end of said spring being secured to the end of said guideway adjacent said rotatable member.

2. A brush holder for a dynamoelectric machine comprising an open ended housing for receiving a carbon brush, a pressure finger assembly for urging said brush into contact with a rotatable member, said pressure finger assembly including a flexible pressure finger overlying said brush and bearing thereon when in operative position to urge said brush toward said rotatable member, a movable carrier for said pressure finger, a stationary guideway for said carrier, a substantially constant force spring terminating in a self-rewinding volute, said volute being mounted on said carrier and the free end of said spring being secured to the end of said guideway adjacent said rotatable member and means for re a taining said carrier and said'pressure'finger in inoperative position and out of engagement with said brush.

3*.- A; brush holder for a dynamoelectric machine com prising an open ended housing for receiving a brush, a pressure finger assembly for urging said brush into contact with a rotatable member, said pressure finger assembly including a flexible pressure finger overlying said brush and bearing thereon when in operative position to urge said brush toward said rotatable member, a movable carrier for said pressure finger, a stationary guideway for said carrier terminating in a laterally disposed surface, a substantially constant force spring terminating in a self-rewinding volute, said volute being mounted on said carrier and the free end of said spring being secured to the end of said guideway adjacent said rotatable member, and means on said laterally disposed surface for retaining said carrier and said pressure finger in inoperative position and out of engagement with said brush.

4. A brush holder for a dynamoelectric machine com prising an open ended housing for receiving a brush, a pressure finger assembly for urging said brush into contact with a rotatable member, said pressure finger assembly including a flexible pressure finger overlying said brush and bearing thereon when in operative position to urge said brush toward said rotatable member, a movable carrier for said pressure finger, a stationary guideway for said carrier terminating in a laterally disposed surface at its end remote from said rotatable member, a transverse recess in said lateral surface, a roller on said carrier engaging said guideway and extending transversely thereof, biasing means on said carrier for urging said pressure finger into engagement with said brush, said roller being receivable in said recess to retain said pressure finger in inoperative position and out of engagement with said brush.

5. A brush holder for a dynamoelectric machine comprising an open ended housing for receiving a brush, a pressure finger assembly for urging said brush into contact with a rotatable member, said pressure finger assembly including a flexible pressure finger overlying said brush and bearing thereon when in operative position to urge said brush toward said rotatable member, a movable carrier for said pressure finger, a stationary guideway for said carrier terminating in a laterally disposed surface at its end remote from said rotatable member, a transverse recess in said lateral surface, a roller on said carrier engaging said guideway and extending transversely thereof, spring means mounted at one end on said carrier and at its other end on said guideway for biasing said pressure 8 finger into operative position in engagement with said brush, said roller being receivable in said recess to retain said pressure finger in inoperative position and out of engagement with said brush.

6. A brush holder for a dynamoelectric machine com prising an open ended housing for receiving a brush, a pressure finger assembly for urging said brush into contact with a rotatable member, said pressure finger assembly including a flexible pressure finger overlying said brush and bearing thereon when in operative position to urge said brush toward said rotatable member, a movable carrier for said pressure finger, a stationary guideway for said carrier terminating in a laterally disposed surface at its end remote from said rotatable member, a transverse recess in said lateral surface, a roller on said carrier engaging said track and extending transversely thereof, a substantially constant force spring terminating in a selfrewinding volute, said volute being mounted on said carrier and the free end of said spring being secured to the end of said guideway adjacent said rotatable member, said roller being receivable in said recess to retain said pressure-finger in inoperative position and out of engagement with said brush.

7. A brush holder for a dynamoelectric machine comprising an open ended housing for receiving a brush, a longitudinally extending, stationary guideway disposed substantially parallel to said housing, a carrier movable on said guideway, a flexible pressure finger rigidly secured to said carrier, said pressure finger overlying said brush and bearing thereon when in operative position, constant force means lior biasing said carrier to urge said pressure finger into engagement with said brush.

8. A brush holder for a dynamoelectric machine comprising an open ended housing for receiving a brush, a pressure finger assembly for urging said brush into contact with a rotatable member, said pressure finger assembly including a flexible pressure finger overlying said brush and bearing thereon when in operative position to urge said brush toward said rotatable member, a movable carrier for said pressure finger, a stationary guideway for said carrier, and a substantially constant force spring terminating in a self-rewinding volute, said volute being mounted on said carrier and the free end of said spring being secured to said guideway.

Priest Dec. 6, 1904 Huber Nov. 25, 1958 

